1. Technical Field
The present invention relates to a reference voltage circuit of a simple configuration such that a predetermined reference voltage can be stably generated, regardless of power supply voltage fluctuation or temperature change.
2. Background Art
Reference voltage circuits that generate a predetermined reference voltage are widely used in various kinds of electronic circuit as circuits that regulate threshold voltage set in, for example, a comparator, and the like. As this kind of reference voltage circuit, it is proposed that a depletion type MOSFET (metal-oxide-semiconductor field-effect transistor) 1 and an enhancement type MOSFET 2 are combined as shown in, for example, FIG. 13, and a reference voltage Vref is generated utilizing the difference between the threshold voltages of the MOSFETs 1 and 2 (refer to Japanese Patent No. 4,765,168). However, a reference voltage circuit disclosed in Japanese Patent No. 4,765,168 is such that it is necessary to form the depletion type MOSFET 1 in addition to the enhancement type MOSFET 2 on a circuit element substrate, because of which there is a problem in that the cost of the manufacturing process thereof, and the like, soars.
Meanwhile, there is also a reference voltage circuit constructed to include multiple enhancement type MOSFETs 3a to 3d, which form a current mirror circuit and carry out a constant current operation, and multiple bipolar transistors 4a to 4d connected in series to the MOSFETs 3a to 3d respectively, as shown in FIG. 14 (refer to Japanese Patent Application No. JP-A-2009-48464). The reference voltage circuit disclosed in JP-A-2009-48464, by utilizing constant voltage operation at the base-emitter voltage of each of the bipolar transistors 4a to 4d, generates a constant reference voltage Vref from the output of the current mirror circuit, regardless of fluctuation in a power supply voltage Vcc.